Method and device for processing a gas containing hydrogen sulfide and sulfur dioxide comprising a stage of removal of by-products

ABSTRACT

A method for processing a gas containing at least hydrogen sulfide (H 2 S) and at least sulfur dioxide (SO 2 ), includes the steps of contacting the gas with a liquid solvent containing at least one catalyst in a contacting stage, recovering gaseous effluent substantially containing no hydrogen sulfide and no sulfur dioxide from the contacting stage, and separating liquid sulfur from liquid solvent in a decantation zone downstream of the contacting stage. In order to remove by-products resulting from degradation of the catalyst, a liquid fraction F containing at least solvent, catalyst, sulfur and the solid by-products resulting from degradation of the catalyst is extracted from after the contacting stage. The liquid fraction F is sent to a processing stage distinct from the contacting stage where the liquid fraction F is heated to a temperature at least partially crystallizing the by-products, and the at least partially crystallized by-products separated from the rest of the liquid fraction F containing at least solvent. At least a stream F 1  comprising solvent, catalyst and sulfur and substantially free of the by-products and a stream F 2  mostly comprising the by-products are recovered.

FIELD OF THE INVENTION

[0001] The object of the present invention is a method for processing,by means of an organic solvent containing at least one catalyst, agaseous effluent containing at least hydrogen sulfide and sulfurdioxide, during which most of the by-products formed during saidtreating process is removed.

[0002] The by-product removal stage, or processing stage, is notablycarried out at a temperature allowing formation and growth of thecrystals of these by-products, i.e. crystallization of theseby-products.

[0003] The method according to the invention is for example applied inClauspol processing units used after the Claus process.

BACKGROUND OF THE INVENTION

[0004] The Claus process is widely used, notably in refineries (afterhydrodesulfurization or catalytic cracking units) and for processing ofnatural gas, to recover elemental sulfur from gaseous feeds containinghydrogen sulfide. However, the fumes produced by Claus plants contain,even after several catalytic stages, appreciable amounts of acid gases.It is then necessary to process these Claus plant effluents (tail gas)to remove most of the toxic compounds so as to abide by antipollutionstandards.

[0005] It is for example well-known to recover about 95% by weight ofthe sulfur present from a Claus plant.

[0006] Processing this Claus plant effluent with a Clauspol plant allowsfor example to reach 99.8% by weight of solvent recovered, from theexothermic Claus reaction:

2H₂S+SO₂

3S+2H₂O   (reaction 1)

[0007] Such processing requires a reaction medium consisting of anorganic solvent and at least one catalyst comprising an alkaline oralkaline-earth salt of an organic acid. Contacting the gas to beprocessed and the organic solvent containing the catalyst is carried outin a gas-liquid contactor reactor whose temperature is controlled bypassage of the solvent, that has been extracted from the contactorreactor by a circulation pump, into a heat exchanger so as to favour thehighest sulfur conversion coefficient while preventing formation ofsolid sulfur. It is well-known that, in this type of plant, the solventthat has a limited capacity for dissolving elemental sulfur becomesloaded with free liquid elemental sulfur that can be separated from thesolvent by simple decantation. This liquid sulfur—solvent decantation iscarried out in a liquid-liquid decantation zone that can be situated atthe bottom of the contactor reactor. The sulfur is thus recovered inliquid form.

[0008] Operation of such a plant is for example described in one of thefollowing reference books:

[0009] Y. BARTHEL, H. GRUHIER, The IFP Clauspol 1500 process: eightyears of industrial experience, Chem. Eng. Monogr., 10 (Large Chem.Plants), 1979, pp.69-86;

[0010] HENNICO A., BARTHEL Y., BENAYOUN D., DEZAEL C., Clauspol 300: thenew IFP TGT process, For presentation at AIChE Summer National Meeting,Denver (Colo.), Aug. 14-17, 1994.

[0011] It is furthermore well-known that the desulfurization rate of aplant of this type can be improved by desaturating the solvent in sulfurin a desaturation loop according to a process described in patentFR-2,735,460 filed by the applicant. In this case, part of thesingle-phase solvent and sulfur solution extracted at the end of thecontactor reactor is cooled in order to crystallize the sulfur. Thiscrystallized sulfur is then separated from the solvent by various knownsolid-liquid separation means such as filtration, decantation orcentrifugation. A sulfur-depleted solvent that can be recycled to thecontactor reactor is obtained on the one hand, and a suspension enrichedin solid sulfur that can be reheated to melt the sulfur, then sent to asolvent-sulfur liquid-liquid decantation zone where the liquid sulfur isrecovered is obtained on the other hand.

[0012] Although such a method proves to be effective, it can however belimited.

[0013] For example, side reactions occur in the contactor reactor,leading to formation of by-products, mainly salts such as alkaline oralkaline-earth sulfates or thiosulfates, due for example to the slowdegradation of the catalyst. These by-products tend to accumulate in thedecantation zone at the interface between the organic solvent and theliquid sulfur, which makes decantation of the liquid sulfur difficult.

[0014] One way allowing to overcome this problem is described in patentFR-2,735,460, which discloses the possibility of passing a solventcontaining such salts through a filter. The salts settle on the filter,and the sulfur-containing solvent is sent to a sulfur-desaturationstage. On the one hand, such processing of the circulating solvent isnot sufficient to entirely remove any accumulation of these salts at theliquid sulfur-solvent interface, including the liquid sulfur-solventdecantation zone situated downstream from the zone intended for sulfurdesaturation of the solvent. On the other hand, if the solvent is notdesaturated in sulfur by means of a desaturation loop, sulfur might beco-eliminated with the solid salts, so that processing of the fluidresulting from regeneration of the filter will be delicate.

SUMMARY OF THE INVENTION

[0015] The object of the present invention is a method and itsassociated device, wherein a solution extracted from the contactorreactor and containing at least solvent, catalyst, sulfur andby-products is subjected to at least one heating stage and to at leastone separation stage so as to remove most of the by-products it containsand to obtain a solvent practically free of said by-products.

[0016] These by-products are for example the result of the slowdegradation of the catalyst.

[0017] It has been observed that heating the fluid extracted from thecontactor reactor and containing at least solvent, catalyst, sulfur andby-products to a suitable temperature:

[0018] favours crystallization of the by-products in solution in thesolvent, which facilitates removal of said by-products,

[0019] causes solubilization of the free sulfur droplets possiblypresent in the solvent, which prevents co-elimination of sulfur with theby-products and facilitates the possible processing of the fluidresulting from regeneration of elements in the processing zone.

[0020] The solvent practically free of by-products can be advantageouslyrecycled, partly or totally, to the contactor reactor where the gas isprocessed.

[0021] The invention relates to a method for processing a gas containingat least hydrogen sulfide (H₂S) and at least sulfur dioxide (SO₂),wherein said gas is contacted, at a suitable temperature, with anorganic solvent containing at least one catalyst, a gaseous effluentsubstantially containing no hydrogen sulfide and no sulfur dioxide anymore is recovered, as well as liquid sulfur separated from the solventby liquid-liquid decantation.

[0022] It is characterized in that:

[0023] a fluid F containing at least solvent, catalyst, sulfur andby-products is extracted after the contacting stage,

[0024] said fluid F is sent to a processing stage comprising at leastone heating stage during which said fluid F is brought to a determinedtemperature favouring crystallization of the by-products, and to a stageof separation of the by-products from the solvent,

[0025] after the processing stage, at least a stream F₁ comprisingmainly solvent, catalyst and sulfur and nearly free of by-products and astream F₂ comprising most of the by-products are recovered.

[0026] Fluid F is for example a liquid single-phase solution.

[0027] The by-products contained in fluid F can be dissolved and/orcrystallized.

[0028] The temperature to which said fluid F is brought ranges forexample between 120 and 180° C., preferably between 120 and 150° C.

[0029] The processing stage is for example carried out by implementingat least one of the following procedures:

[0030] a) carrying out at least one filtering stage so as to recoversaid fluid F₁ mainly consisting of solvent depleted in solid by-productsand said fluid F₂ resulting from regeneration of the filtering supportand containing most of the by-products, and/or

[0031] b) carrying out at least one stage of capture, on a solidsupport, of the by-products so as to recover at least said fluid F₁mainly consisting of solvent depleted in by-products and said fluid F₂resulting from regeneration of the solid support and containing most ofthe by-products.

[0032] Procedures a) and b) can be carried out at a temperature rangingbetween 120 and 180° C., preferably between 120 and 150° C.

[0033] Fluid F₁ resulting from the processing stage can be recycled,partly or totally, to the contacting stage.

[0034] The invention also relates to a device allowing to remove and torecover by-products formed during a process for treating a gaseouseffluent containing at least hydrogen sulfide (H₂S) and sulfur dioxide(SO₂) wherein a solvent and at least one catalyst are used, said devicecomprising at least one contactor reactor, at least one decantationzone, several lines for delivery of at least the gas to be processed, ofthe solvent and of the catalyst, several lines for extraction of atleast a cleaned gas and of a fluid containing at least solvent,catalyst, sulfur and by-products.

[0035] It is characterized in that it comprises at least one zone forprocessing said fluid comprising at least solvent, catalyst, sulfur andby-products, said processing zone including heating means suited tofavour crystallization of the by-products and by-products—solventseparation means. At the outlet of the processing zone, at least a fluidF₁ mainly consisting of solvent, catalyst and sulfur and nearly free ofby-products and a fluid F₂ containing most of the by-products arerecovered.

[0036] The heating means are operated for example between 120 and 180°C., preferably between 120 and 150° C.

[0037] According to an embodiment, the decantation zone is situated inthe lower part of said contactor reactor.

[0038] The processing zone can comprise at least one of the separationmeans selected from the following means:

[0039] filtering means, said means being suited to produce at leastfluid F₁ mainly consisting of solvent and at least fluid F₂ containingmost of the by-products formed, and/or

[0040] capture means such as metals, activated charcoals, zeolites,resins, aluminas, silicas or ceramics, said means being suited toproduce at least fluid F₁ mainly consisting of solvent and at leastfluid F₂ containing most of the by-products formed.

[0041] The device can comprise a line allowing to recycle at least partof the solvent coming from the processing stage, or fluid F₁, to thecontactor reactor.

[0042] The contactor reactor is for example selected from one of thedevices mentioned in the following list: reactor with random or stackedpacking or static mixer SMV or impactor or hydro-ejector or atomizer orwire contactor.

[0043] The method and the device according to the invention are forexample applied for processing effluents from Claus plants processingthe H₂S coming from natural gas scrubbing operations or from crude oilrefining operations.

[0044] The method and its associated device notably afford the followingadvantages:

[0045] they allow to prevent problems of decantation of the liquidsulfur in the liquid-liquid decantation zone,

[0046] they allow to prevent accumulation of solid by-products in thepackings provided in certain contactor reactor types,

[0047] they allow to simply improve existing Clauspol plants by mereaddition of a small number of equipments and therefore at a low cost,

[0048] they allow to recover a cleaned solvent and to recycle itdirectly to the gas treating process.

BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Other features and advantages of the invention will be clear fromreading the description hereafter of several embodiments of the method,with reference to the accompanying simplified and non limitativedrawings wherein:

[0050]FIG. 1 is a block diagram of the various elements that constitutethe device according to the invention, notably the processing zone,

[0051]FIG. 2 illustrates a gas processing device comprising adecantation zone situated in the lower part of a contactor reactor,

[0052]FIG. 3 diagrammatically shows a variant where the processing zoneis a filtering zone,

[0053]FIG. 4 diagrammatically shows a variant where the processing zoneis a capture mass, and

[0054]FIG. 5 shows a diagram from the prior art given by way ofcomparative example.

DETAILED DESCRIPTION OF THE INVENTION

[0055] The embodiments given hereafter by way of non limitative examplerelate to the removal of the by-products formed during processing of agas containing at least hydrogen sulfide and sulfur dioxide. Theseby-products are notably due to the slow degradation of the catalyst usedin the gas treating process.

[0056] According to FIG. 1, the device comprises a gas-liquid contactorreactor 1. A line 2 supplies the contactor reactor with asulfur-containing gas feed, for example an effluent from a Claus plant,and a line 3 delivers for example a recycled solution comprising asolvent such as polyethylene glycol 400 and a catalyst such as sodiumsalicylate.

[0057] Various solvents and catalysts selected from the list given inthe description hereafter can be used without departing from the scopeof the invention.

[0058] The cleaned gas is discharged through a line 4.

[0059] A fluid F such as a solvent solution containing at leastcatalyst, sulfur and by-products formed is discharged from contactorreactor 1 through a line 5. This solution is then sent through a pump 6and lines 7 and 13 to a processing zone 14 where it is freed of most ofthe by-products. Processing zone 14 comprises at least heating means andseparation means some of which are shown in detail in FIGS. 3 and 4. Theheating means are suited to obtain a temperature favouringcrystallization of the by-products in solution in the solvent. Anydevice known to the man skilled in the art and allowing to obtain and towork at this temperature, notably allowing to reach crystallization ofthe by-products formed as mentioned above can be used.

[0060] The means for heating the solvent in the processing zone aresuited to work within a temperature range between 120 and 180° C.,preferably between 120 and 150° C.

[0061] The function of processing zone 14, comprising means (not shownin this figure) for heating the solvent solution and means (not shown inthis figure) for separating the by-products from the solvent, is notablyto process solution F containing notably solvent, catalyst, sulfur andby-products, in order to obtain at least a fluid F₂ containing most ofthe by-products that is discharged through line 19, and a fluid F₁consisting mainly of solvent practically totally free of by-products,that is for example recycled through line 15 to contactor reactor 1.

[0062] Fluid F₁, in the form OF a liquid single-phase solution nearlyfree of by-products, is sent through lines 15 and 7 into a heatexchanger 8 where it is cooled to a suitable temperature compatible withoperation of contactor reactor 1, 120° C. for example. This temperaturecan be controlled by means of a regulator 9 connected to heat exchanger8 by a line 10. Line 10 is for example connected to a valve 11 withwhich a line 12 intended for delivery of the coolant in the heatexchanger is equipped. This cooled solvent solution from heat exchanger8 can be recycled to contactor reactor 1 through line 3.

[0063] Fluid F₂ comprising most of the by-products and dischargedthrough line 19 is for example diluted in water prior to being sent towater treatment.

[0064] The liquid sulfur obtained by decantation is discharged through aline 18 situated in the lower part of decantation zone 17, connected tocontactor reactor 1 by a line 16. Line 18 is provided with a valve V₁for example.

[0065] the temperature range selected can also allow solubilization ofthe free sulfur droplets possibly present in the solvent. this has theeffect of preventing removal of the sulfur with the by-products formedand of facilitating possible processing of the fluid resulting fromregeneration of the elements in the processing zone.

[0066]FIG. 2 diagrammatically shows a realisation variant where thedecantation zone is included in contactor reactor 1.

[0067] The reference numbers are the same as those used for theidentical elements shown in FIG. 1.

[0068] The lower part of contactor reactor 1 comprises a decantationzone 17′ provided with a liquid sulfur extraction line 18, the linebeing for example equipped with a valve V₁ similar to that shown in FIG.1.

[0069] Part of the single-phase solvent solution that circulates in therecycle loop (notably consisting of elements 5, 6, 7, 8, 3), for example10 to 20% of the solution, is for example extracted through a line 40,from line 7, in order to be sent to a processing zone such as a zone 41for desaturating the solvent in sulfur.

[0070] In this desaturation zone 41, the single-phase solution iscooled, for example to 60° C., in order to form a suspension of sulfurcrystals in the solvent. This crystallized sulfur is then separated fromthe solvent by means of various solid-liquid separation processes knownto the man skilled in the art, such as filtering, decantation orcentrifugation. A sulfur-depleted solvent is obtained on the one handand extracted through a line 42 in order to be recycled for example tocontactor reactor 1, and a suspension enriched in solid sulfur isobtained on the other hand. The suspension enriched in solid sulfur canbe reheated by appropriate means known to the man skilled in the art inorder to melt the sulfur, then sent through a line 43 to theliquid-liquid decantation zone.

[0071] In the various realisation variants given in this description,the operating conditions of the process and of the device can be asfollows:

[0072] Contactor reactor 1 can be operated at a temperature ranging forexample between 50 and 130° C., preferably between 120 and 122° C. Saidsulfur formed is in the liquid form. The liquid sulfur formed is hardlysoluble in the solvent and, because of its higher density, it settles inthe bottom of the reactor. The water formed is discharged with thecleaned gas. Under such conditions (low temperature and continuousremoval of the products formed), equilibrium (1) is displaced to theright. This temperature is for example controlled by passage of thesolvent in heat exchanger 8.

[0073] The process can be carried out within a very wide pressure range,9.8 kPa to 4.9 MPa for example. According to an embodiment, it iscarried out at the atmospheric pressure.

[0074] The contactor reactor can consist of any equipment or series ofequipments allowing contacting of a gas and of a liquid. It can forexample be selected from the following list of equipments:

[0075] Reactor with random (Intalox saddles for example) or stackedpacking (Mellapak type for example) marketed by the Sulzer company forexample,

[0076] Static mixer SMV marketed by the Sulzer company for example,

[0077] Impactor marketed by the AEA company for example,

[0078] Hydro-ejector marketed by the Biotrade company for example,

[0079] Atomizer marketed by the LAB company for example,

[0080] Wire contactor marketed by the Toussaint Nyssenne company forexample.

[0081] The solvents commonly used are mono- or poly-alkylene glycols,mono- or poly-alkylene glycol esters or mono- or poly-alkylene glycolethers, as described in patents FR-2,115,721 (U.S. Pat. No. 3,796,796),FR-2,122,674 and FR-2,138,371 (U.S. Pat. No. 3,832,454).

[0082] the catalysts used are selected from those mentioned in thesepatents and more particularly alkaline salts of weak organic acids suchas benzoic acid and salicylic acid.

[0083] The concentration of the catalyst in the liquid phaseadvantageously ranges between 0.1 and 5% by weight, more advantageouslybetween 0.5 and 2% by weight.

[0084] The method and the device according to the invention areparticularly well-suited for processing a gas whose acid gas content(H₂S+SO₂) ranges between 0.1 and 100% by volume. It is howeverparticularly advantageous for gases having a low acid gas content(H₂S+SO₂), for example between 0.1 and 50% by volume, and moreparticularly between 0.5 and 5% by volume.

[0085] The separation stage in zone 14 can be performed in various ways,some of which are given hereafter by way of non limitative example.

[0086] Filtering Processing

[0087] According to a variant illustrated in FIG. 3, processing zone 14comprises heating means 20 and filtration separation means 22.

[0088] The solvent solution F extracted from contactor reactor 1 throughline 5 is sent through pump 6 and lines 7 (FIG. 2) and 13 to processingzone 14 comprising a heat exchanger 20 and filtering means, for exampleone or more filters 22, each consisting for example of at least onedeformable cloth filter cartridge 23.

[0089] The solution is heated in heat exchanger 20 to a temperatureranging between 120 and 150° C. in order to favour crystallization ofthe by-products in solution in the solvent and to solubilize the freesulfur droplets possibly present in the solvent. The solution is thenpassed into filter 22 where the solid by-products settle on cartridge 23whereas the cleaned solvent F₁ is extracted through line 15 in order tobe recycled to the top of contactor reactor 1.

[0090] Clearing of cartridge 23 in order to eliminate the depositedsolid by-products is for example performed by isolating filter 22 fromthe rest of the device and by sending into cartridge 23 a fluid such asfiltered solvent or water, introduced at a pressure slightly higher thanthe atmospheric pressure through a line 24. The clearing operation canbe required when the thickness of the cake formed is such that thepressure difference on the filtering cartridge becomes high, for examplebetween 0.1 and 0.4 MPa.

[0091] The by-products in solution in the clearing fluid are extractedfrom the bottom of the filter through a line 19.

[0092] The means allowing to isolate processing zone 14 from the rest ofthe processing circuit are known to the man skilled in the art and arenot detailed. They notably include isolating valves V₂.

[0093] At least a second filter acting as a by-pass filter or parallelto the first one can be provided to ensure continuous filtering of thesolvent solution when the first filter is being cleared.

[0094] Capture Processing

[0095] According to a variant illustrated in FIG. 4, separation of theby-products formed is carried out in processing zone 14 by capture on asolid support.

[0096] The solvent solution discharged from contactor reactor 1 throughline 5 is sent through pump 6 and lines 7 (FIG. 2) and 13 to processingzone 14 comprising a heat exchanger 20 and capture means, for exampleone or more capacities 25 comprising each one or more capture beds 26.The beds consist of solids, for example metals, activated charcoals,zeolites, resins, aluminas, silicas or ceramics.

[0097] The solution is heated in heat exchanger 20 to a temperatureranging between 120 and 150° C. notably in order to favourcrystallization of the by-products in solution in the solvent and tosolubilize the free sulfur droplets possibly present in the solvent. Thesolvent solution introduced through line 21 into capacity 25 is passedthrough collecting bed 26 which traps the by-products. The solvent freedof the most part of the by-products is discharged from capacity 25through line 15 in order to be recycled to contactor reactor 1.

[0098] When the bed is saturated with solid by-products, capacity 25 isisolated from the rest of the device and clean water introduced througha line 27 is for example passed through bed 26. The water is dischargedthrough a line 19, loaded with dissolved by-products. According to thesolid support used, saturation can be controlled either by measuring thepressure drop in the bed or by extrapolating saturation curves obtainedin the laboratory.

[0099] As in the case of filtering, the means allowing to isolateprocessing zone 14 from the rest of the processing circuit are known tothe man skilled in the art and will not be detailed. They notablycomprise isolating valves V₃.

[0100] At least a second capacity acting as a by-pass capacity can beprovided to allow continuous capture of the by-products contained in thesolvent solution during regeneration or replacement of the bed of thefirst capacity.

[0101] Two numerical examples given hereafter allow to better understandthe advantages afforded by the different variants of the methodaccording to the invention.

[0102] In these examples, the term “salt” designates the by-productslikely to be formed notably by side reactions because of the presence ofthe catalyst during a gas treating process.

[0103] The two examples given differ in their method of separation ofthe by-products and the solvent. In both cases, the contactor reactor isoperated as follows:

[0104] A tail gas from a Claus plant is fed through a line 2, at a flowrate of 12300 Nm³/h, into a vertical contactor reactor 1 consisting of acolumn containing two packing beds, and it is contacted at 125° C. withan organic solvent containing a soluble catalyst introduced through line3.

[0105] The packing used in both examples consists of 2 saddle beds(“Intalox” ceramic saddles 250 m²/m³ in specific surface).

[0106] The organic solvent used is a polyethylene glycol with amolecular mass of 400 and the soluble catalyst is sodium salicylate at aconcentration of 100 millimoles/kg solvent.

[0107] The solvent is recycled between the bottom and the top of thecontactor reactor through lines 5, 7 and 3 at a flow rate of 500 m³/h,by means of circulation pump 6 through a heat exchanger 8, temperaturecontrol and regulation being provided by a measuring and control system9, 10 and 11 allowing hot water to be injected at 80° C. into theexchanger through line 12. The temperature of the recycled solvent is125° C.

[0108] The cleaned gas flows out of the contactor reactor through line4. The sulfur formed settles at the bottom of the contactor reactor andis extracted through line 18 at a rate of 332 kg/h.

[0109] The compositions of the gases flowing into and out of the plantare given in the table hereafter: Incoming gas (2) Outgoing gas (4)Constituents % vol. % vol. H₂S 1.234 0.0586 SO₂ 0.617 0.0293 CO₂ 4.0004.038 COS 0.015 0.009 CS₂ 0.015 0.009 S_(v)* 0.14 0.03 N₂ 60 60.396 H₂O34 35.384 Sum of the sulfur compounds 2.036 0.1449 (counted in sulfur)

[0110] The sulfur compounds yield in the contactor reactor is:${\frac{\begin{matrix}\left( {{\% \quad {incoming}\quad {sulfur}\quad {compounds}} -} \right. \\\left. {\% \quad {outgoing}\quad {sulfur}\quad {compounds}} \right)\end{matrix}}{\% \quad {incoming}\quad {sulfur}\quad {compounds}} \times 100} = {{\frac{\left( {2.036 - 0.1449} \right)}{2.036} \times} = {92.9\%}}$

[0111] The total yield of the 97% yield Claus plant+Clauspol finishingplant is:${97 + \frac{\left( {3 \times 92.9} \right)}{100}} = {99.8\%}$

[0112] The solution F extracted through line 5 is processed by filteringor capture in processing zone 14 according to the two proceduresdescribed hereafter.

EXAMPLE 1 (FIGS. 2 and 3): Filtration Separation

[0113] Heat exchanger 20 allows to heat the solvent solution to 135° C.and a filter 22 consisting of three 1-m² surface cartridges 23 allows toseparate the two fluids F₁ and F₂. Clearing is performed by isolatingprocessing zone 14 from the rest of the device and by sending waterunder slight pressure into the cartridges through line 24 when thethickness of the cake exceeds 3 mm, i.e. when the pressure difference onthe filtering cartridges becomes greater than 0.2 MPa. After clearing,the salts are recovered in solution in the water at the bottom of thefilter and sent to water treatment through line 19. The filter iscleared about every 12 h.

EXAMPLE 3 (FIGS. 2 and 4): Capture Separation

[0114] In this example, heat exchanger 20 allows to heat the solventsolution to 135° C. and a capacity 25 containing two 1-m³ salt capturebeds 26, each made of a material having a good affinity with the saltsto be collected, ceramic saddles for example, allows to separate fluidsF₁ and F₂. After one month of continuous running, the pressure dropbecomes higher than 7 kPa, which indicates that the beds are saturatedwith salts. The processing zone is then isolated from the rest of thedevice and the capture beds are regenerated by washing with waterintroduced clean through line 27 and discharged loaded with saltsthrough line 19 prior to being sent to water treatment.

[0115]FIG. 5 diagrammatically shows the process according to the priorart wherein fluid F, or single-phase solution containing mainly solvent,catalyst, sulfur and by-products, is extracted through line 5 anddirectly sent into a heat exchanger 30 similar to exchanger 8, prior tobeing recycled to the contactor reactor. Temperature control isperformed in the same way as in FIG. 1, with a regulator 9 connected toheat exchanger 30 by a line 10, the coolant being delivered through aline 12 equipped with a valve 11 and discharged through a line 13.

1. A device to remove and recover by-products formed during processingof a gaseous effluent containing at least hydrogen sulfide (H₂S) andsulfur dioxide (SO₂), wherein an organic solvent and at least onecatalyst are used, said device comprising at least one contactorreactor, at least one decantation zone, several lines for delivery of atleast a gas to be processed, of a fluid comprising at least solvent andcatalyst, several lines for extraction of at least a cleaned gas and ofa fluid F containing at least solvent, catalyst, sulfur and by-products,at least a processing zone for processing said fluid F comprising atleast solvent, catalyst, sulfur and by-products, said processing zonecomprising heating means suited to favour crystallization of theby-products and separation means suited to separate the by-products fromthe rest of said fluid comprising at least solvent, catalyst and sulfur,and at least a fluid F₁ containing mainly solvent, catalyst and sulfurand nearly free of by-products and a fluid F₂ comprising most of theby-products are recovered at the outlet of said processing zone.
 2. Adevice as claimed in claim 1 , characterized in that heating means arefor example operated between 120 and 180° C., preferably between 120 and150° C.
 3. A device as claimed in claim 1 , characterized in thatdecantation zone is situated in the lower part of said contactorreactor.
 4. A device as claimed in claim 1 , characterized in that theprocessing zone can comprise at least one of the means selected from thegroup consisting of: filtering means for producing at least fluid F₁containing mainly solvent and nearly free of by-products, and at leastfluid F₂ containing most of the by-products formed, and capture meansfor producing at least fluid F₁ containing mainly solvent and nearlyfree of by-products, and at least fluid F₂ containing most of theby-products formed.
 5. A device as claimed in claim 1 , characterized inthat it comprises a line allowing to recycle at least part of thesolvent from the processing stage to the contactor reactor.
 6. A deviceas claimed in claim 1 , characterized in that said contactor reactor isselected from the group consisting of a reactor with random or stackedpacking, a static mixer SMV, an impactor, a hydro-ejector, an atomizer,and a wire contactor.
 7. A device as claimed in claim 1 , wherein saiddevice is connected to a Claus plant processing H₂S from natural gasscrubbing operation or crude oil refining operations, and said gaseouseffluent is an effluent of the Claus plant.